This invention relates to a filter suitable for use in a cartridge for the preparation of a beverage and to the cartridge provided with this filter.
Swiss patent 605 293 relates to a cartridge for the preparation of a beverage, particularly espresso coffee, consisting of a fluid-tight body generally frustoconical in shape with a border at its base, a membrane closing the base and a filter adjacent the membrane.
The filter used is a 0.04 to 0.06 mm mesh screen of polypropylene. This filter has a number of disadvantages which make it far from attractive. Its weldability is not good. It shows poor mechanical strength during extraction of the cartridge, being deformed or tearing at the edges under the effect of a pressure of up to 15 bar. It presents crimping problems during production of the cartridge. That is, the edges are not completely fluid-tight, thus posing problems affecting the keeping properties of the coffee due to the entry of oxygen into the cartridge. Finally, the quality of the coffee obtained is not satisfactory, in that, the extraction level of the coffee is not optimized, nor is the quality of the froth typical of espresso coffee.